Pentatonic refers to any scale or chord with five notes, but usually refers to the pentatonic scale, a very consonant scale that is the complement of the diatonic scale. The scale consists of whole-tone steps and minor thirds.
The set class (unordered collection of notes) of the pentatonic scale is maximally even and has five modes. Every transposition of the diatonic scale shares five notes (a pentatonic scale) with two neighboring diatonic scales on the circle of fifths. Therefore each of the twelve transpositions of the pentatonic scale shares all of its notes with three diatonic scales, and each diatonic scale shares five notes with three different pentatonic scales.